DDT Is Still Evident in Soil and Crops 12 Years After Being Prohibited

Nearly 13 years after it was banned, the potent pesticide DDT persists in soils throughout the state, and detectable--but reportedly safe--levels are continuing to show up in vegetables, the state Department of Food and Agriculture said Monday.

At one of three sites tested in Orange County, concentrations of DDT compounds were 17 times higher than the highest levels previously found in sediment samples in the San Diego Creek watershed, which drains most of the county’s current and historic agricultural acreage.

With mussels in Newport Bay already showing the highest saltwater levels of DDT ever recorded in California, regional water quality and environmental officials have embarked on separate studies to track the source of the banned pesticide.

But the agriculture department said there was no evidence that DDT is being used illegally, as some had suspected.

Residues Being Blamed

“Based on all available evidence, the California Department of Food and Agriculture concluded that long-lived residues from previous applications are the apparent source of DDT residues in produce and in the environment,” the report said.

A department spokeswoman added that the concentration of 2.958 parts per million of DDT compounds found at the undisclosed Orange County location do not translate into a threat to public health, although the state Department of Health Services has set an action level of 1.0 ppm for declaring an area a toxic waste site.

“What these results mean simply is that Orange County is right along with the rest of the counties in California where we are finding DDT is stabilized in the soil,” said Ronald J. Oshima, chief of environmental monitoring for the agriculture department.

“For counties in general,” Oshima said, “it means that finding DDT in the soil is not a good indication that DDT is being newly applied.”

Within Acceptable Levels

DDT was detected in crops in which an edible portion grows in, or close to, the ground, such as carrots, beets, lettuce and spinach. The department said that “in most cases,” the contamination was well within acceptable levels. The contamination was believed to be caused in large part by DDT-laced soil on the plant’s surface, not within the plant’s system.

Rinsing the produce with water may further reduce DDT levels, the department said.

In a yearlong study ordered by the Assembly, in part because of suspicions of clandestine use of DDT by some growers, the department found widespread DDT levels throughout California’s principal agricultural areas.

Indeed, the report said, DDT was detected in all 99 soil samples taken in 32 counties. The department concluded that half of all the DDT used before it was prohibited at the end of 1972 is still in the environment and may remain in California soil for 12 to 15 more years.

“The important role that DDT has played in California agriculture cannot be diminished or denied. Equally important, however, is the legacy of long-term, widespread environmental contamination which the usage of DDT has left us,” the report said.

The report was generally applauded Monday by the office of Assemblyman Lloyd Connelly (D-Sacramento) and by a scientist with the Natural Resource Defense Council in San Francisco. Connelly wrote the resolution calling for the study.

Feed Question Unanswered

However, both Connelly’s office and the environmental group pointed out that DDT principally accumulates in fatty tissue of fish and animals rather than in leafy crops. But the department study failed to list what, if any, DDT levels were found in feed grain that is eaten by beef cattle and milk-producing cows.

Lawrie Mott, a senior project scientist with the Natural Resource Defense Council, added that the report failed to adequately examine the role of a DDT substitute known as dicofol in possibly adding new levels of DDT to the environment. The federal Environmental Protection Agency has found the level of DDT in dicofol to be 10% before it is formulated into commercial pesticides.

The department report concluded that dicofol use in California “is not a significant source of DDT residues.” However, the finding was based only on a limited sampling. Dicofol is used on cotton, fruits and vegetables, as well as on lawns.

DDT usage in California began about 1944 and reached a peak in 1970, the last year in which substantial amounts were applied to crops. DDT is still widely used in developing countries.

3 Sources Studied

The study investigated three possible sources in an attempt to explain the continued presence of DDT: new illegal use, use of other pesticides containing DDT, and long-lived residues from previous legal use of DDT.

In addition to taking soil samples, investigators also reviewed a 1984 study of DDT-residue levels in fish and mussels in Monterey County’s Salinas River.

In Orange County, the concentration of DDT and its breakdown compounds in soil samples ranged from a low of .321 ppm to a high of 2.958 ppm. Exact locations of the three sites were not immediately available Monday, but Oshima said the areas may no longer be under cultivation.

When alarming levels of DDT and other chemicals began turning up in mussels and small bait fish in Newport Bay from 1979 to 1984, the California Regional Water Quality Control Board, the state Department of Fish and Game and county health officials began looking upstream for a source of DDT.

Last January, sediment samples from 22 locations along the San Diego Creek watershed turned up varying concentrations of DDT and its breakdown compounds.

The highest concentration of .166 ppm of total DDT compounds was found in a county flood control channel near Irvine Center Drive and Sand Canyon Avenue, in an area of citrus, avocado and row crops, and wholesale nurseries. The highest level of what appeared to be active DDT was .045 ppm found in the Barranca Channel in Irvine.

‘Hot Spots’ Resampled

All were well below the National Academy of Sciences toxic threshold of 1.0 ppm for fish and wildlife. But the findings prompted the regional board and county health officials to resample five “hot spot” areas.

Joanne E. Schneider, the board’s environmental specialist working on the project, said Monday that sediment samples gathered last summer have been discarded because of problems with laboratory test results. She said new samples would be gathered early next year, after the winter rains.

Schneider said she was unaware of the agriculture department findings.

Frank Parsons, Orange County’s deputy agricultural commissioner, said Monday that the state Food and Agriculture Department conclusion that DDT persists longer than expected in the soil appears to parallel local findings.

After the regional board’s sediment samples turned up what appeared to be active DDT, Parsons said foliage and crop tests were sampled in the same areas.

“We found no DDT in the foliage or the crops we sampled,” Parsons said. “We had already checked the pesticide storage areas to make certain no illegal DDT was being stored. We also checked spray applicators to make sure there was no residue of DDT.”